Helldritch
Hero
All mega dungeons started in OD&D and were later adapted for AD&D. That is why so many adventures of "basic" D&D could be played with AD&D without modification. The reverse was not true however...I have it for 5e. But I don't think this group of players particularly likes megadungeons.
Do megadungeons even work in Basic/OSR? Like, I would think the entire game mechanic of combat, rest, recovery would breakdown very quickly.